How important is a virus protection program in Linux.

I read on one hand that virus protection isn't really required because
it is extremely hard to crack Linux due to all the natural security
afforded by the different run levels.

On the other hand, I see articles about "root kits" as a threat, and
virtualization attacks.

I know just about enough to get a decent install on my system, and
have no real idea as to whether the immunity statement is outdated and
wishful thinking, or the root kit stuff is hype and overblown in an
effort to get us to buy protection we will never need.

Your thoughts?